$ F = \left[\begin{array}{rr}-2 & 4 \\ -1 & -1 \\ 1 & 1 \\ 2 & 3\end{array}\right]$ What are the dimensions of matrix $ F$ ?
The first dimension is the number of rows in the matrix. How many rows does $ F$ have? The second dimension is the number of columns in the matrix. How many columns does $ F$ have? So, $ F$ is a 4 $\times$ 2 matrix.